In a 3rd Generation Partnership Project (3GPP, 3rd Generation Partnership Project) radio access network (RAN, Radio Access Network) technology of a cellular communication system, four coordinated multi-point transmission (CoMP, Coordinated Multi-Point Transmission) scenarios are defined. In a third CoMP scenario (briefly known as CoMP solution 3), a cell identity (Cell Identity) is allocated to each RRH at a transmission point of a transceiver, that is, abase station or a radio remote head (RRH, Radio Remote Head), in the area of a macro site. Such a structure is similar to a system where multiple base stations coexist. However, in a fourth CoMP scenario (briefly known as CoMP solution 4), the same cell identity is shared by all transmission points of a transceiver, that is, a base station or a radio remote head, in the area of a macro site. Such an architecture is also called a distributed antenna system (DAS, Distributed Antenna System).
In an existing relevant standard, a real-life multiple-input multiple-output (Real-life Multiple-Input Multiple-Output) antenna configuration scenario is defined, that is, one user equipment (UE, User Equipment) may be combined with one or more antennas of transceivers located in different geographic positions to form a MIMO system, thereby implementing a distributed downlink or uplink MIMO system.
In uplink transmission of a DAS system and a system similar to a system where multiple base stations coexist, uplink power control is generally applied to a UE to achieve roughly the same level of the receive power when different types of user equipments arrive at a base station (BS, Base Station), so as to avoid interference between users caused by a near-far effect. In a 3GPP Long Term Evolution (LTE, Long Term Evolution) Release-10 standard, the transmit power of a physical uplink shared channel (PUSCH, Physical Uplink Shared Channel), a physical uplink control channel (PUCCH, Physical Uplink Control Channel), and an uplink sounding reference signal (SRS, Sounding Reference Signal) is determined by a path loss (PL, Path Loss) estimated by the UE, as expressed by the following formula:PLc=referenceSignalPower−RSRP
where, referenceSignalPower is reference signal power defined for the base station, and is obtained by the UE by receiving or sensing cell-based higher layer signaling (Higher layer signaling) sent by the base station, and RSRP is reference signal receive power measured by the UE at a common reference signal (CRS, Common Reference Signal) port (Port0 or Port1).
However, the existing PL calculation method can only be used for calculating a path loss from the user equipment to one base station, and cannot be used for calculating a path loss from the user equipment to multiple transceivers.
Three uplink power control solutions in a CoMP system have been put forward in the prior art: Solution 1 is a PL compensation solution based on a current serving cell, solution 2 is a maximum value solution based on a CoMP receiving point, and solution 3 is a solution based on a nonlinear averaging method. Without fully considering a path condition of each of multiple uplink power transmission points, solutions 1, 2, and 3 are incapable of calculating a path loss of multiple uplink power transmission points accurately, and are therefore incapable of performing accurate uplink power control.
In addition, a CRS-based open-loop power control (OLPC, Open-loop power control) solution exists in the prior art. The uplink path loss obtained by using the CRS-based open-loop power control solution is not accurate enough, and therefore, this solution is incapable of performing accurate uplink power control.
In the process of implementing the present invention, the inventor of the present invention finds that the uplink actual receiving point may be inconsistent with the downlink actual receiving point, and therefore, the path loss calculation varies between the uplink and the downlink. The existing CoMP solutions 3 and 4 and the PL calculation method for a real-life MIMO system can only be used for calculating the path loss from the user equipment to one base station, and cannot be used for calculating the path loss from the user equipment to multiple base stations or RRHs. Moreover, in a communication system equipped with one or more RRHs, multiple paths exist in both downlink transmission and uplink transmission, which makes the uplink path loss calculation rather complicated. None of the existing solutions is capable of calculating the uplink path loss accurately. Therefore, it is necessary to work out an uplink power control method for calculating the path loss of multiple uplink paths and controlling uplink power.